Heat exchanger

ABSTRACT

A heat exchanger includes: flat pipes vertically arrayed and fins that partition a space between adjacent ones of the flat pipes into air flow passages. Each of the flat pipes includes a passage for a refrigerant. The flat pipes are divided into heat exchange sections. Each of the heat exchange sections includes: a main heat exchange section connected to a gas-side entrance communication space, and a sub heat exchange section that is connected in series to the main heat exchange section at a vertical position different from the main heat exchange section and to a liquid-side entrance communication space.

TECHNICAL FIELD

The present invention relates to a heat exchanger. In particular, thepresent invention relates to a heat exchanger including a plurality offlat pipes vertically arrayed, each of the flat pipes including apassage for a refrigerant formed inside thereof, and a plurality of finsthat partition a space between adjacent flat pipes into a plurality ofair flow passages through which air flows.

BACKGROUND

In a conventional technique, a heat exchanger including a plurality offlat pipes vertically arrayed and a plurality of fins that partition aspace between adjacent flat pipes into a plurality of air flow passagesthrough which air flows may be employed as a heat exchanger housed in anoutdoor unit (heat exchange unit) of an air conditioner. Further, forexample, such a heat exchanger includes a heat exchanger as described inPatent Literature 1 (JP 2012-163313 A) in which a plurality of flatpipes are divided into a plurality of heat exchange sections which arevertically arranged side by side, and each of the heat exchange sectionsincludes a main heat exchange section and a sub heat exchange sectionwhich is connected in series to the main heat exchange section below themain heat exchange section.

PATENT LITERATURE

Patent Literature 1: JP 2012-163313 A

The above conventional heat exchanger may be employed in an airconditioner that performs a heating operation and a defrosting operationin a switching manner. When the air conditioner performs the heatingoperation, the above conventional heat exchanger is used as anevaporator for a refrigerant. When the air conditioner performs thedefrosting operation, the above conventional heat exchanger is used as aradiator for the refrigerant. Specifically, when the above conventionalheat exchanger is used as the evaporator for the refrigerant, therefrigerant in a gas-liquid two-phase state is divided and flows intothe sub heat exchange section included in each heat exchange section, isheated while passing through the sub heat exchange section and the mainheat exchange section in that order, and flows out of the heat exchangesection. Then, flows of the refrigerant merge with each other. Further,when the above conventional heat exchanger is used as the radiator forthe refrigerant, the refrigerant in a gas state is divided and flowsinto the main heat exchange section of each heat exchange section, iscooled while passing through the main heat exchange section and the subheat exchange section in that order, and flows out of the heat exchangesection. Then, flows of the refrigerant merge with each other.

However, in the air conditioner that employs the above conventional heatexchanger, the time required for melting frost adhered to the lowermostheat exchange section tends to become longer than the time required formelting frost adhered to the heat exchange section located on the upperside relative to the lowermost heat exchange section in the defrostingoperation. Thus, frost may remain unmelted in the lowermost heatexchange section even after the defrosting operation, which may resultin insufficient defrosting. Further, it is necessary to increase thetime of the defrosting operation in order to suppress frost fromremaining unmelted in the lowermost heat exchange section.

SUMMARY

One or more embodiments of the present invention shorten the timerequired for melting frost adhered to the lowermost heat exchangesection in a defrosting operation of a heat exchanger that includes aplurality of flat pipes vertically arrayed, each of the flat pipesincluding a passage for a refrigerant formed inside of the flat pipe,and a plurality of fins that partition a space between each adjacent twoof the flat pipes into a plurality of air flow passages through whichair flows is employed in an air conditioner that performs a heatingoperation and a defrosting operation in a switching manner.

A heat exchanger according to one or more embodiments includes aplurality of flat pipes vertically arrayed, each of the flat pipesincluding a passage for a refrigerant formed inside of the flat pipe;and a plurality of fins that partition a space between each adjacent twoof the flat pipes into a plurality of air flow passages through whichair flows. The flat pipes are divided into a plurality of heat exchangesections, and each of the heat exchange sections includes a main heatexchange section connected to a gas-side entrance communication spaceand a sub heat exchange section connected in series to the main heatexchange section at a vertical position different from the main heatexchange section and connected to a liquid-side entrance communicationspace. Further, when one of the heat exchange sections including alowermost one of the flat pipes is defined as a first heat exchangesection, and the main heat exchange section and the sub heat exchangesection that constitute the first heat exchange section are defined as afirst main heat exchange section and a first sub heat exchange section,the first main heat exchange section is disposed so as to include thelowermost flat pipe.

First, the reason why the time required for melting frost adhered to thelowermost heat exchange section tends to become longer than the timerequired for melting frost adhered to the heat exchange section locatedon the upper side relative to the lowermost heat exchange section in thedefrosting operation when the above conventional heat exchanger isemployed in an air conditioner that performs the heating operation andthe defrosting operation in a switching manner will be described.

In the above conventional heat exchanger, a plurality of flat pipes aredivided into a plurality of heat exchange sections which are verticallyarranged side by side, and each of the heat exchange sections includes amain heat exchange section and a sub heat exchange section which isconnected in series to the main heat exchange section below the mainheat exchange section. Thus, in the above conventional heat exchanger,the sub heat exchange section of the lowermost one of the heat exchangesections is disposed so as to include the lowermost flat pipe.

In the conventional configuration, when the heating operation (used asthe evaporator for the refrigerant) is switched to the defrostingoperation (used as the radiator for the refrigerant), the refrigerant ina liquid state tends to be accumulated in the lowermost sub heatexchange section including the lowermost flat pipe. Further, when thedefrosting operation is performed in such a condition, the refrigerantin a gas state first flows into the lowermost main heat exchange sectionand then flows into the lowermost sub heat exchange section. Thus, ittakes long time to evaporate the refrigerant in a liquid stateaccumulated in the lowermost sub heat exchange section. That is, it isassumed that, in the configuration of the conventional heat exchanger,the lowermost sub heat exchange section including the lowermost flatpipe located on the downstream side in the refrigerant flow in thedefrosting operation is one of the reasons why the time required formelting frost adhered to the lowermost heat exchange section becomeslong in the defrosting operation.

Further, in this configuration, when the refrigerant in a gas state isdivided and flows into the main heat exchange section of each heatexchange section in the defrosting operation, a flow rate of therefrigerant in a gas state flowing into the lowermost heat exchangesection becomes lower than that in the upper heat exchange section dueto the influence of a liquid head of the refrigerant, which increasesthe time required for melting frost adhered to the lowermost heatexchange section. The degree of the liquid head is affected by theheight position of the flat pipe included in the sub heat exchangesection of the heat exchange section. Thus, when the lowermost sub heatexchange section includes the lowermost flat pipe, the liquid head ofthe refrigerant is large, and the flow rate of the refrigerant in a gasstate flowing into the lowermost heat exchange section in the defrostingoperation is further reduced. That is, it is assumed that, in theconfiguration of the conventional heat exchanger, a reduction in theflow rate of the refrigerant in a gas state flowing into the lowermostheat exchange section due to the liquid head of the refrigerant in thedefrosting operation is one of the reasons why the time required formelting frost adhered to the lowermost heat exchange section becomeslong in the defrosting operation.

Further, in the conventional configuration, the lower end part of thefin close to the lowermost flat pipe is in contact with a drain pan.Thus, heat dissipation from the lowermost sub heat exchange sectionincluding the lowermost flat pipe to the drain pan tends to occur. Whenthe defrosting operation is performed in such a condition, heatdissipation from the lowermost sub heat exchange section to the drainpan hinders a temperature rise in the lowermost heat exchange section ascompared to the upper heat exchange section, which increases the timerequired for melting frost adhered to the lowermost heat exchangesection. That is, it is assumed that, in the configuration of theconventional heat exchanger, heat dissipation from the lowermost subheat exchange section including the lowermost flat pipe to the drain panis one of the reasons why the time required for melting frost adhered tothe lowermost heat exchange section becomes long in the defrostingoperation.

In this manner, it is assumed that, in the conventional heat exchanger,when the heat exchanger is employed in the air conditioner that performsthe heating operation and the defrosting operation in a switchingmanner, the time required for melting frost adhered to the lowermostheat exchange section is longer than the time required for melting frostadhered to the heat exchange section located on the upper side relativeto the lowermost heat exchange section because the lowermost sub heatexchange section includes the lowermost flat pipe.

Thus, in one or more embodiments, differently from the conventional heatexchanger, as described above, the first main heat exchange section ofthe first heat exchange section including the lowermost flat pipe amongthe heat exchange sections is disposed so as to include the lowermostflat pipe.

Further, when the heat exchanger having such a configuration is employedin the air conditioner that performs the heating operation and thedefrosting operation in a switching manner, the refrigerant in agas-liquid two-phase state flows into the first sub heat exchangesection, is heated while passing through the first sub heat exchangesection and the first main heat exchange section including the lowermostflat pipe in that order, and flows out of the first heat exchangesection in the heating operation (used as the evaporator for therefrigerant) when attention is paid to the first heat exchange section.Further, in the defrosting operation (used as the radiator for therefrigerant), the refrigerant in a gas state flows into the first mainheat exchange section, is cooled while passing through the first mainheat exchange section including the lowermost flat pipe and the firstsub heat exchange section in that order, and flows out of the first heatexchange section. That is, in one or more embodiments, the first mainheat exchange section including the lowermost flat pipe is located onthe upstream side in the refrigerant flow in the defrosting operation.Thus, in one or more embodiments, it is possible to allow therefrigerant in a gas state to flow into the first main heat exchangesection including the lowermost flat pipe to actively heat and evaporatethe refrigerant in a liquid state accumulated in the lowermost first subheat exchange section and promptly increase the temperature in thelowermost first heat exchange section. Accordingly, in one or moreembodiments, it is possible shorten the time required for melting frostadhered to the lowermost heat exchange section in the defrostingoperation as compared to the case where the conventional heat exchangeris employed.

In this manner, in one or more embodiments, it is possible to shortenthe time required for melting frost adhered to the lowermost heatexchange section in the defrosting operation by employing the heatexchanger having the above configuration in the air conditioner thatperforms the heating operation and the defrosting operation in aswitching manner.

According to one or more embodiments, all the heat exchange sectionsother than the first heat exchange section are disposed above the firstheat exchange section. Further, the first main heat exchange section isdisposed below the first sub heat exchange section in the first heatexchange section.

When the heat exchanger having such a configuration is employed in theair conditioner that performs the heating operation and the defrostingoperation in a switching manner, the refrigerant in a gas-liquidtwo-phase state flows into the first sub heat exchange section, isheated while passing through the first sub heat exchange section and thefirst main heat exchange section located below the first sub heatexchange section in that order, and flows out of the first heat exchangesection in the heating operation (used as the evaporator for therefrigerant) when attention is paid to the first heat exchange section.Further, in the defrosting operation (used as the radiator for therefrigerant), the refrigerant in a gas state flows into the first mainheat exchange section, is cooled while passing through the first mainheat exchange section and the first sub heat exchange section locatedabove the first main heat exchange section in that order, and flows outof the first heat exchange section.

According to one or embodiments, a ratio of a number of the flat pipesconstituting the first main heat exchange section to a number of theflat pipes constituting the first sub heat exchange section is setsmaller than a ratio of a number of the flat pipes constituting the mainheat exchange section to a number of the flat pipes constituting the subheat exchange section in the other heat exchange sections.

As described above, the heat exchanger according to one or moreembodiments includes the first heat exchange section in which the firstmain heat exchange section is disposed below the first sub heat exchangesection. Thus, when the heat exchanger according to one or moreembodiments is employed in the air conditioner that performs the heatingoperation and the defrosting operation in a switching manner, the firstheat exchange section functions as a so-called down flow type evaporatorin which the refrigerant passes through the first sub heat exchangesection and then passes through the first main heat exchange sectiondisposed below the first sub heat exchange section in the heatingoperation (used as the evaporator for the refrigerant). In the down flowtype evaporator, when a fluid in a gas-liquid two-phase state is dividedwhen being fed downward, a drift of the fluid tends to occur. Also inthe first heat exchange section, the refrigerant is divided when beingfed downward from the flat pipes constituting the first sub heatexchange section to the flat pipes constituting the first main heatexchange section. Thus, there is a possibility that a drift of therefrigerant occurs. At this time, when the ratio of the number of theflat pipes constituting the first main heat exchange section to thenumber of the flat pipes constituting the first sub heat exchangesection increases, the possibility of the occurrence of a drift of therefrigerant increases.

Thus, in one or more embodiments, as described above, in the first heatexchange section, the ratio of the number of the flat pipes constitutingthe main heat exchange section to the number of the flat pipesconstituting the sub heat exchange section is set smaller than that inthe other heat exchange sections.

Accordingly, in one or more embodiments, when the refrigerant is feddownward from the flat pipes constituting the first sub heat exchangesection to the flat pipes constituting the first main heat exchangesection in the heating operation (used as the evaporator for therefrigerant), it is possible to suppress a drift of the refrigerantcaused by the division of the refrigerant.

According to one or more embodiments, all the heat exchange sectionsother than the first heat exchange section are disposed above the firstheat exchange section. Further, the first sub heat exchange sectionincludes a first upper sub heat exchange section and a first lower subheat exchange section located below the first upper sub heat exchangesection. In addition, the first main heat exchange section includes afirst upper main heat exchange section connected to the first upper subheat exchange section above the first upper sub heat exchange sectionand a first lower main heat exchange section connected to the firstlower sub heat exchange section below the first lower sub heat exchangesection.

When the heat exchanger having such a configuration is employed in theair conditioner that performs the heating operation and the defrostingoperation in a switching manner, the refrigerant in a gas-liquidtwo-phase state flows into the first upper sub heat exchange section andthe first lower sub heat exchange section in the heating operation (usedas the evaporator for the refrigerant) when attention is paid to thefirst heat exchange section. Then, the refrigerant in a gas-liquidtwo-phase state flowing into the first upper sub heat exchange sectionis heated while passing through the first upper sub heat exchangesection and the first upper main heat exchange section located above thefirst upper sub heat exchange section in that order, and flows out ofthe first heat exchange section. The refrigerant in a gas-liquidtwo-phase state flowing into the first lower sub heat exchange sectionis heated while passing through the first lower sub heat exchangesection and the first lower main heat exchange section located below thefirst lower sub heat exchange section in that order, and flows out ofthe first heat exchange section. Further, in the defrosting operation(used as the radiator for the refrigerant), the refrigerant in a gasstate flows into the first upper main heat exchange section and thefirst lower main heat exchange section. Then, the refrigerant in a gasstate flowing into the first upper main heat exchange section is cooledwhile passing through the first upper main heat exchange section and thefirst upper sub heat exchange section located below the first upper mainheat exchange section in that order, and flows out of the first heatexchange section. The refrigerant in a gas state flowing into the firstlower main heat exchange section is cooled while passing through thefirst lower main heat exchange section and the first lower sub heatexchange section located above the first lower main heat exchangesection in that order, and flows out of the first heat exchange section.

According to one or more embodiments, a number of the flat pipesconstituting the first lower main heat exchange section to a number ofthe flat pipes constituting the first lower sub heat exchange section isset smaller than a ratio of a number of the flat pipes constituting thefirst upper main heat exchange section to a number of the flat pipesconstituting the first upper sub heat exchange section.

As described above, the heat exchanger according to one or moreembodiments includes the first heat exchange section in which the firstupper sub heat exchange section is disposed below the first upper mainheat exchange section, and the first lower main heat exchange section isdisposed below the first lower sub heat exchange section. Thus, when theheat exchanger according to one or more embodiments is employed in theair conditioner that performs the heating operation and the defrostingoperation in a switching manner, the first lower sub heat exchangesection and the first lower main heat exchange section in the first heatexchange section function as a so-called down flow type evaporator inwhich the refrigerant passes through the first lower sub heat exchangesection and then passes through the first lower main heat exchangesection disposed below the first lower sub heat exchange section in theheating operation (used as the evaporator for the refrigerant). In thedown flow type evaporator, when a fluid in a gas-liquid two-phase stateis divided when being fed downward, a drift of the fluid tends to occur.Also in the first lower sub heat exchange section and the first lowermain heat exchange section, the refrigerant is divided when being feddownward from the flat pipes constituting the first lower sub heatexchange section to the flat pipes constituting the first lower mainheat exchange section. Thus, there is a possibility that a drift of therefrigerant occurs. At this time, when the ratio of the number of theflat pipes constituting the first lower main heat exchange section tothe number of the flat pipes constituting the first lower sub heatexchange section increases, the possibility of the occurrence of a driftof the refrigerant increases.

Thus, in one or more embodiments, as described above, the ratio of thenumber of the flat pipes constituting the first lower main heat exchangesection to the number of the flat pipes constituting the first lower subheat exchange section is set smaller than the ratio of the number of theflat pipes constituting the first upper main heat exchange section tothe number of the flat pipes constituting the first upper sub heatexchange section in the first heat exchange section.

Accordingly, in one or more embodiments, when the refrigerant is feddownward from the flat pipes constituting the first lower sub heatexchange section to the flat pipes constituting the first lower mainheat exchange section in the heating operation (used as the evaporatorfor the refrigerant), it is possible to suppress a drift of therefrigerant caused by the division of the refrigerant.

According to one or more embodiments, the heat exchange sections arevertically arranged side by side, and the sub heat exchange section isdisposed below the main heat exchange section in the heat exchangesections other than the first heat exchange section.

When the heat exchanger having such a configuration is employed in theair conditioner that performs the heating operation and the defrostingoperation in a switching manner, the refrigerant in a gas-liquidtwo-phase state flows into the sub heat exchange section, is heatedwhile passing through the sub heat exchange section and the main heatexchange section located above the sub heat exchange section in thatorder, and flows out of the heat exchange section in the heatingoperation (used as the evaporator for the refrigerant) when attention ispaid to the heat exchange sections other than the first heat exchangesection. Further, in the defrosting operation (used as the radiator forthe refrigerant), the refrigerant in a gas state flows into the mainheat exchange section, is cooled while passing through the main heatexchange section and the sub heat exchange section located below themain heat exchange section in that order, and flows out of the heatexchange section.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic configuration diagram of an air conditioner thatemploys an outdoor heat exchanger as a heat exchanger according to oneor more embodiments of the present invention.

FIG. 2 is an external perspective view of an outdoor unit.

FIG. 3 is a front view of the outdoor unit (except refrigerant circuitconstituent components other than the outdoor heat exchanger).

FIG. 4 is a schematic perspective view of the outdoor heat exchanger.

FIG. 5 is a partial enlarged perspective view of heat exchange sectionsof FIG. 4.

FIG. 6 is a schematic configuration diagram of the outdoor heatexchanger.

FIG. 7 is a table listing a schematic configuration of the outdoor heatexchanger.

FIG. 8 is an enlarged view near the lowermost heat exchange section (thefirst heat exchange section) of FIG. 6 (illustrating the flow of arefrigerant in a heating operation).

FIG. 9 is an enlarged view near the lowermost heat exchange section (thefirst heat exchange section) of FIG. 6 (illustrating the flow of therefrigerant in a defrosting operation).

FIG. 10 is a schematic perspective view of an outdoor heat exchanger asa heat exchanger according to a modification.

FIG. 11 is a schematic configuration diagram of the outdoor heatexchanger according to the modification.

FIG. 12 is a table listing a schematic configuration of the outdoor heatexchanger according to the modification.

FIG. 13 is an enlarged view near the lowermost heat exchange section(the first heat exchange section) of FIG. 11 (illustrating the flow of arefrigerant in a heating operation).

FIG. 14 is an enlarged view near the lowermost heat exchange section(the first heat exchange section) of FIG. 11 (illustrating the flow ofthe refrigerant in a defrosting operation).

DETAILED DESCRIPTION

Hereinbelow, embodiments and modifications of a heat exchanger accordingto the present invention will be described with reference to thedrawings. A specific configuration of the heat exchanger according toone or more embodiments of the present invention is not limited to theembodiments and the modifications described below, and can be changedwithout departing from the gist of the invention.

(1) Configuration of Air Conditioner

FIG. 1 is a schematic configuration diagram of an air conditioner 1 thatemploys an outdoor heat exchanger 11 as a heat exchanger according toone or more embodiments of the present invention.

The air conditioner 1 is an apparatus capable of performing cooling andheating inside a room of a building or the like by preforming a vaporcompression refrigeration cycle. The air conditioner 1 mainly includesan outdoor unit 2, indoor units 3 a, 3 b, a liquid-refrigerantconnection pipe 4 and a gas-refrigerant connection pipe 5 which connectthe outdoor unit 2 to the indoor units 3 a, 3 b, and a control unit 23which controls constituent devices of the outdoor unit 2 and the indoorunits 3 a, 3 b. A vapor compression refrigerant circuit 6 of the airconditioner 1 is formed by connecting the outdoor unit 2 to the indoorunits 3 a, 3 b through the refrigerant connection pipes 4, 5.

The outdoor unit 2 is installed outside the room (on a roof of abuilding, near a wall surface of a building or the like), andconstitutes a part of the refrigerant circuit 6. The outdoor unit 2mainly includes an accumulator 7, a compressor 8, a four-way switchingvalve 10, an outdoor heat exchanger 11, an outdoor expansion valve 12 asan expansion mechanism, a liquid-side shutoff valve 13, a gas-sideshutoff valve 14, and an outdoor fan 15. These devices and valves areconnected through refrigerant pipes 16 to 22.

The indoor units 3 a, 3 b are installed inside the room (in a livingroom, in a ceiling space or the like), and constitute a part of therefrigerant circuit 6. The indoor unit 3 a mainly includes an indoorexpansion valve 31 a, an indoor heat exchanger 32 a, and an indoor fan33 a. The indoor unit 3 b mainly includes an indoor expansion valve 31 bas an expansion mechanism, an indoor heat exchanger 32 b, and an indoorfan 33 b.

The refrigerant connection pipes 4, 5 are constructed in a site wherethe air conditioner 1 is installed in an installation place such as abuilding. One end of the liquid-refrigerant connection pipe 4 isconnected to the liquid-side shutoff valve 13 of the indoor unit 2, andthe other end of the liquid-refrigerant connection pipe 4 is connectedto liquid-side ends of the indoor expansion valves 31 a, 31 b of theindoor units 3 a, 3 b. One end of the gas-refrigerant connection pipe 5is connected to the gas-side shutoff valve 14 of the indoor unit 2, andthe other end of the gas-refrigerant connection pipe 5 is connected togas-side ends of the indoor heat exchangers 32 a, 32 b of the indoorunits 3 a, 3 b.

Control unit 23 is configured by control boards or the like (notillustrated) included in the outdoor unit 2 and the indoor units 3 a, 3b being communicably connected to the control unit 23. In FIG. 1, forconvenience, the control unit 23 is separated from the outdoor unit 2and the indoor units 3 a, 3 b. The control unit 23 controls theconstituent devices 8, 10, 12, 15, 31 a, 31 b, 33 a, 33 b of the airconditioner 1 (in one or more embodiments, the outdoor unit 2 and theindoor units 3 a, 3 b), that is, controls driving of the entire airconditioner 1.

(2) Operation of Air Conditioner

Next, the operation of the air conditioner 1 will be described withreference to FIG. 1. The air conditioner 1 performs a cooling operationwhich circulates a refrigerant through the compressor 8, the outdoorheat exchanger 11, the outdoor expansion valve 12, the indoor expansionvalves 31 a, 31 b, and the indoor heat exchangers 32 a, 32 b in thatorder and a heating operation which circulates the refrigerant throughthe compressor 8, the indoor heat exchangers 32 a, 32 b, the indoorexpansion valves 31 a, 31 b, the outdoor expansion valve 12, and theoutdoor heat exchanger 11 in that order. In the heating operation, adefrosting operation for melting frost adhered to the outdoor heatexchanger 11 is performed. In one or more embodiments, an inversed cycledefrosting operation which circulates the refrigerant through thecompressor 8, the outdoor heat exchanger 11, the outdoor expansion valve12, the indoor expansion valves 31 a, 31 b, and the indoor heatexchangers 32 a, 32 b in that order in a manner similar to the coolingoperation is performed. The control unit 23 performs the coolingoperation, the heating operation, and the defrosting operation.

In the cooling operation, the four-way switching valve 10 is switched toan outdoor heat dissipation state (a state indicated by a solid line inFIG. 1). In the refrigerant circuit 6, a low-pressure gas refrigerant ofthe refrigeration cycle is sucked into the compressor 8, compresseduntil the refrigerant becomes high pressure of the refrigeration cycle,and then discharged. The high-pressure gas refrigerant discharged fromthe compressor 8 is fed to the outdoor heat exchanger 11 through thefour-way switching valve 10. The high-pressure gas refrigerant fed tothe outdoor heat exchanger 11 dissipates heat by exchanging heat withoutdoor air which is supplied as a cooling source by the outdoor fan 15to become a high-pressure liquid refrigerant in the outdoor heatexchanger 11 which functions as a radiator for the refrigerant. Thehigh-pressure liquid refrigerant after heat dissipation in the outdoorheat exchanger 11 is fed to the indoor expansion valves 31 a, 31 bthrough the outdoor expansion valve 12, the liquid-side shutoff valve13, and the liquid-refrigerant connection pipe 4. The refrigerant fed tothe indoor expansion valves 31 a, 31 b is decompressed to a low pressureof the refrigeration cycle by the indoor expansion valves 31 a, 31 b tobecome a low-pressure refrigerant in a gas-liquid two-phase state. Thelow-pressure refrigerant in a gas-liquid two-phase state decompressed bythe indoor expansion valves 31 a, 31 b is fed to the indoor heatexchangers 32 a, 32 b. The low-pressure refrigerant in a gas-liquidtwo-phase state fed to the indoor heat exchangers 32 a, 32 b evaporatesby exchanging heat with indoor air which is supplied as a heating sourceby the indoor fans 33 a, 33 b in the indoor heat exchangers 32 a, 32 b.Accordingly, the indoor air is cooled and then supplied into the room,thereby cooling the inside of the room. The low-pressure gas refrigerantevaporated in the indoor heat exchangers 32 a, 32 b is sucked into thecompressor 8 again through the gas-refrigerant connection pipe 5, thegas-side shutoff valve 14, the four-way switching valve 10, and theaccumulator 7.

In the heating operation, the four-way switching valve 10 is switched toan outdoor evaporation state (a state indicated by a broken line in FIG.1). In the refrigerant circuit 6, a low-pressure gas refrigerant of therefrigeration cycle is sucked into the compressor 8, compressed untilthe refrigerant becomes a high pressure of the refrigeration cycle, andthen discharged. The high-pressure gas refrigerant discharged from thecompressor 8 is fed to the indoor heat exchangers 32 a, 32 b through thefour-way switching valve 10, the gas-side shutoff valve 14, and thegas-refrigerant connection pipe 5. The high-pressure gas refrigerant fedto the indoor heat exchangers 32 a, 32 b dissipates heat by exchangingheat with indoor air which is supplied as a cooling source by the indoorfans 33 a, 33 b to become a high-pressure liquid refrigerant in theindoor heat exchangers 32 a, 32 b. Accordingly, the indoor air is heatedand then supplied into the room, thereby heating the inside of the room.The high-pressure liquid refrigerant after heat dissipation in theindoor heat exchangers 32 a, 32 b is fed to the outdoor expansion valve12 through the indoor expansion valves 31 a, 31 b, theliquid-refrigerant connection pipe 4, and the liquid-side shutoff valve13. The refrigerant fed to the outdoor expansion valve 12 isdecompressed to a low pressure of the refrigeration cycle by the outdoorexpansion valve 12 to become a low-pressure refrigerant in a gas-liquidtwo-phase state. The low-pressure refrigerant in a gas-liquid two-phasestate decompressed by the outdoor expansion valve 12 is fed to theoutdoor heat exchanger 11. The low-pressure refrigerant in a gas-liquidtwo-phase state fed to the outdoor heat exchanger 11 evaporates byexchanging heat with outdoor air which is supplied as a heating sourceby the outdoor fan 15 to become a low-pressure gas refrigerant in theoutdoor heat exchanger 11 which functions as an evaporator for therefrigerant. The low-pressure gas refrigerant evaporated in the outdoorheat exchanger 11 is sucked into the compressor 8 again through thefour-way switching valve 10 and the accumulator 7.

When frost formation in the outdoor heat exchanger 11 is detectedaccording to, for example, the temperature of the refrigerant in theoutdoor heat exchanger 11 lower than a predetermined temperature, thatis, when a condition for starting defrosting in the outdoor heatexchanger 11 is satisfied, a defrosting operation for melting frostadhered to the outdoor heat exchanger 11 is performed.

The defrosting operation is performed by switching the four-wayswitching valve 22 to the outdoor heat dissipation state (the stateindicated by the solid line in FIG. 1) to cause the outdoor heatexchanger 11 to function as the radiator for the refrigerant in a mannersimilar to the cooling operation. Accordingly, frost adhered to theoutdoor heat exchanger 11 can be melted. The defrosting operation isperformed until a defrosting time, which is set taking intoconsideration a state of the heating operation before defrosting,elapses or until it is determined that defrosting in the outdoor heatexchanger 11 has been completed according to the temperature of therefrigerant in the outdoor heat exchanger 11 higher than thepredetermined temperature, and the operation then returns to the heatingoperation. The flow of the refrigerant in the refrigerant circuit 10 inthe defrosting operation is similar to that in the cooling operation.Thus, description thereof will be omitted.

(3) Configuration of Outdoor Unit

FIG. 2 is an external perspective view of the outdoor unit 2. FIG. 3 isa front view of the outdoor unit 2 (except the refrigerant circuitconstituent components other than the outdoor heat exchanger 11). FIG. 4is a schematic perspective view of the outdoor heat exchanger 11. FIG. 5is a partial enlarged view of heat exchange sections 60A to 60F of FIG.4. FIG. 6 is a schematic configuration diagram of the outdoor heatexchanger 11. FIG. 7 is a table listing a schematic configuration of theoutdoor heat exchanger 11. FIG. 8 is an enlarged view near the lowermostheat exchange section (the first heat exchange section 60A) of FIG. 6(illustrating the flow of the refrigerant in the heating operation).FIG. 9 is an enlarged view near the lowermost heat exchange section (thefirst heat exchange section 60A) of FIG. 6 (illustrating the flow of therefrigerant in the defrosting operation).

<Overall Configuration>

The outdoor unit 2 is a top blow-out type heat exchange unit that sucksair from the side face of a casing 40 and blows out air from the topface of the casing 40. The outdoor unit 2 mainly includes the casing 40having a substantially rectangular parallelepiped box shape, the outdoorfan 15 as a fan, the devices 7, 8, 11 including the compressor and theoutdoor heat exchanger, and the refrigerant circuit constituentcomponents which include the valves 10, and 12 to 14 having the four-wayswitching valve and the outdoor expansion valve and the refrigerantpipes 16 to 22 and constitute a part of the refrigerant circuit 6. Inthe following description, “up”, “down”, “left”, “right”, “front”,“back”, “front face”, and “back face” indicate directions in a casewhere the outdoor unit 2 illustrated in FIG. 2 is viewed from the front(the diagonally left front side) unless otherwise noted.

The casing 40 mainly includes a bottom frame 42 which is put across apair of installation legs 41 which extend in the right-left direction,supports 43 which extend in the vertical direction from corners of thebottom frame 42, a fan module 44 which is attached to the upper ends ofthe supports 43, and a front panel 45. The casing 40 includes inletports 40 a, 40 b, 40 c for air on the side faces (in one or moreembodiments, the back face, and the right and left side faces) and ablow-out port 40 d for air on the top face.

The bottom frame 42 forms the bottom face of the casing 40. The outdoorheat exchanger 11 is disposed on the bottom frame 42. The outdoor heatexchanger 11 is a heat exchanger which has a substantially U shape inplan view and faces the back face and the right and left side faces ofthe casing 40. The outdoor heat exchanger 11 substantially forms theback face and the right and left side faces of the casing 40. The bottomframe 42 is in contact with a lower end part of the outdoor heatexchanger 11, and functions as a drain pan which receives drain watergenerated in the outdoor heat exchanger 11 in the cooling operation andthe defrosting operation.

The fan module 44 is disposed on the upper side of the outdoor heatexchanger 11 to form a part of the front face, the back face, and theright and left faces of the casing 40 above the supports 43 and the topface of the casing 40. The fan module 44 is an aggregate including asubstantially rectangular parallelepiped box body whose upper and lowerfaces are open and the outdoor fan 15 housed in the box body. Theopening on the top face of the fan module 44 corresponds to the blow-outport 40 d. A blow-out grille 46 is disposed on the blow-out port 40 d.The outdoor fan 15 is disposed facing the blow-out port 40 d inside thecasing 40. The outdoor fan 15 is a fan that takes air into the casing 40through the inlet ports 40 a, 40 b, 40 c and discharges air through theblow-out port 40 d.

The front panel 45 is put between the supports 43 on the front face sideto form the front face of the casing 40.

The refrigerant circuit constituent components other than the outdoorfan 15 and the outdoor heat exchanger 11 (FIG. 2 illustrates theaccumulator 7 and the compressor 8) are also housed inside the casing40. The compressor 8 and the accumulator 7 are disposed on the bottomframe 42.

In this manner, the outdoor unit 2 includes the casing 40 which includesthe inlet ports 40 a, 40 b, 40 c for air formed on the side faces (inone or more embodiments, the back face and the right and left sidefaces) and the blow-out port 40 d for air formed on the top face, theoutdoor fan 15 which is disposed facing the blow-out port 40 d insidethe casing 40, and the outdoor heat exchanger 11 which is disposed belowthe outdoor fan 15 inside the casing 40.

<Outdoor Heat Exchanger>

The outdoor heat exchanger 11 is a heat exchanger that exchanges heatbetween the refrigerant and outdoor air. The outdoor heat exchanger 11mainly includes a first header collecting pipe 80, a second headercollecting pipe 90, a plurality of flat pipes 63, and a plurality offins 64. In one or more embodiments, the first header collecting pipe80, the second header collecting pipe 90, the flat pipes 63, and thefins 64 are all made of aluminum or an aluminum alloy and joined to eachother by, for example, brazing.

Each of the first header collecting pipe 80 and the second headercollecting pipe 90 is a vertically oriented hollow cylindrical memberwhose upper and lower ends are closed. The first header collecting pipe80 stands on one end side (in one or more embodiments, on the left frontend side in FIG. 4 or the left end side in FIG. 6) of the outdoor heatexchanger 11. The second header collecting pipe 90 stands on the otherend side (in one or more embodiments, the right front end side in FIG. 4or the right end side in FIG. 6) of the outdoor heat exchanger 11.

Each of the flat pipes 63 is a flat perforated pipe including a flatpart 63 a which serves as a heat transfer surface and faces in thevertical direction and a large number of small passages 63 b throughwhich the refrigerant flows, the passages 63 b being formed inside theflat pipe 63. A plurality of flat pipes 63 are vertically arrayed. Bothends of each of the flat pipes 63 are connected to the first headercollecting pipe 80 and the second header collecting pipe 90. The fins 64partition a space between adjacent flat pipes 63 into a plurality of airflow passages through which air flows. Each of the fins 64 includes aplurality of cutouts 64 a each of which horizontally extends long sothat a plurality of flat pipes 63 can be inserted into the cutouts 64 a.The shape of the cutout 64 a of the fin 64 substantially coincides withthe outer shape of the cross section of the flat pipe 63.

In the outdoor heat exchanger 11, the flat pipes 63 are divided into aplurality of heat exchange sections 60A to 60F (in one or moreembodiments, six heat exchange sections) which are vertically arrangedside by side. Specifically, in one or more embodiments, a first heatexchange section 60A which is the lowermost heat exchange section, asecond heat exchange section 60B, . . . , a fifth heat exchange section60E, and a sixth heat exchange section 60F are formed in that order frombottom to top. The first heat exchange section 60A includes twenty-oneflat pipes 63 including the lowermost flat pipe 63A. The second heatexchange section 60B includes eighteen flat pipes 63. The third heatexchange section 60C includes fifteen flat pipes 63. The fourth heatexchange section 60D includes thirteen flat pipes 63. The fifth heatexchange section 60E includes eleven flat pipes 63. The sixth heatexchange section 60F includes nine flat pipes 63.

An internal space of the first header collecting pipe 80 is verticallypartitioned by partition plates 81 so that entrance communication spaces82A to 82F respectively corresponding to the heat exchange sections 60Ato 60F are formed. Further, each of the entrance communication spaces82B to 82F except the first entrance communication space 82Acorresponding to the first heat exchange section 60A is verticallypartitioned into two spaces by a partition plate 83 so that uppergas-side entrance communication spaces 84B to 84F and lower liquid-sideentrance communication spaces 85B to 85F are formed. The first entrancecommunication space 82A corresponding to the first heat exchange section60A is vertically partitioned into three spaces by two partition plates86 so that a first upper gas-side entrance communication space 84AU, afirst liquid-side entrance communication space 85A, and a first lowergas-side entrance communication space 84AL are formed in that order fromtop to bottom. The first upper gas-side entrance communication space84AU and the first lower gas-side entrance communication space 84AL arecollectively defined as a first gas-side entrance communication spaces84A.

The second gas-side entrance communication space 84B communicates withtop twelve of the flat pipes 63 constituting the second heat exchangesection 60B. The second liquid-side entrance communication space 85Bcommunicates with the remaining six of the flat pipes 63 constitutingthe second heat exchange section 60B. The third gas-side entrancecommunication space 84C communicates with top ten of the flat pipes 63constituting the third heat exchange section 60C. The third liquid-sideentrance communication space 85C communicates with the remaining five ofthe flat pipes 63 constituting the third heat exchange section 60C. Thefourth gas-side entrance communication space 84D communicates with topnine of the flat pipes 63 constituting the fourth heat exchange section60D. The fourth liquid-side entrance communication space 85Dcommunicates with the remaining four of the flat pipes 63 constitutingthe fourth heat exchange section 60D. The fifth gas-side entrancecommunication space 84E communicates with top seven of the flat pipes 63constituting the fifth heat exchange section 60E. The fifth liquid-sideentrance communication space 85E communicates with the remaining four ofthe flat pipes 63 constituting the fifth heat exchange section 60E. Thesixth gas-side entrance communication space 84F communicates with topsix of the flat pipes 63 constituting the sixth heat exchange section60F. The sixth liquid-side entrance communication space 85F communicateswith the remaining three of the flat pipes 63 constituting the sixthheat exchange section 60F. The first upper gas-side entrancecommunication space 84AU communicates with top twelve of the flat pipes63 constituting the first heat exchange section 60A. The first lowergas-side entrance communication space 84AL communicates with bottom twoof the flat pipes 63 constituting the first heat exchange section 60Aincluding the lowermost flat pipe 63A. The first liquid-side entrancecommunication space 85A communicates with the remaining seven of theflat pipes 63 constituting the first heat exchange section 60A.

The flat pipes 63 communicating with the gas-side entrance communicationspaces 84A to 84F are defined as main heat exchange sections 61A to 61F,and the flat pipes 63 communicating with the liquid-side entrancecommunication spaces 85A to 85F are defined as sub heat exchangesections 62A to 62F. More specifically, in the second entrancecommunication space 82B, the second gas-side entrance communicationspace 84B communicates with top twelve of the flat pipes 63 constitutingthe second heat exchange section 60B (the second main heat exchangesection 61B), and the second liquid-side entrance communication space85B communicates with the remaining six of the flat pipes 63constituting the second heat exchange section 60B (the second sub heatexchange section 62B). In the third entrance communication space 82C,the third gas-side entrance communication space 84C communicates withtop ten of the flat pipes 63 constituting the third heat exchangesection 60C (the third main heat exchange section 61C), and the thirdliquid-side entrance communication space 85C communicates with theremaining five of the flat pipes 63 constituting the third heat exchangesection 60C (the third sub heat exchange section 62C). In the fourthentrance communication space 82D, the fourth gas-side entrancecommunication space 84D communicates with top nine of the flat pipes 63constituting the fourth heat exchange section 60D (the fourth main heatexchange section 61D), and the fourth liquid-side entrance communicationspace 85D communicates with the remaining four of the flat pipes 63constituting the fourth heat exchange section 60D (the fourth sub heatexchange section 62D). In the fifth entrance communication space 82E,the fifth gas-side entrance communication space 84E communicates withtop seven of the flat pipes 63 constituting the fifth heat exchangesection 60E (the fifth main heat exchange section 61E), and the fifthliquid-side entrance communication space 85E communicates with theremaining four of the flat pipes 63 constituting the fifth heat exchangesection 60E (the fifth sub heat exchange section 62E). In the sixthentrance communication space 82F, the sixth gas-side entrancecommunication space 84F communicates with top six of the flat pipes 63constituting the sixth heat exchange section 60F (the sixth main heatexchange section 61F), and the sixth liquid-side entrance communicationspace 85F communicates with the remaining three of the flat pipes 63constituting the sixth heat exchange section 60F (the sixth sub heatexchange section 62F). In the first entrance communication space 82A,the first upper gas-side entrance communication space 84AU, which is oneof the first gas-side entrance communication spaces 84A, communicateswith top twelve of the flat pipes 63 constituting the first heatexchange section 60A (a first upper main heat exchange section 61AUwhich is one of the first main heat exchange sections 61A). Further, inthe first entrance communication space 82A, the first lower gas-sideentrance communication space 84AL, which is the other first gas-sideentrance communication space 84A, communicates with bottom two of theflat pipes 63 constituting the first heat exchange section 60A (a firstlower main heat exchange section 61AL which is the other first main heatexchange section 61A). Further, in the first entrance communicationspace 82A, the first liquid-side entrance communication space 85Acommunicates with the remaining seven of the flat pipes 63 constitutingthe first heat exchange section 60A (the first sub heat exchange section62A).

A liquid-side flow dividing member 70 which divides and feeds therefrigerant fed from the outdoor expansion valve 12 (refer to FIG. 1)into the liquid-side entrance communication spaces 85A to 85F in theheating operation and a gas-side flow dividing member 75 which dividesand feeds the refrigerant fed from the compressor 8 (refer to FIG. 1)into the gas-side entrance communication spaces 84A to 84F in thecooling operation are connected to the first header collecting pipe 80.

The liquid-side flow dividing member 70 includes a liquid-siderefrigerant flow divider 71 which is connected to the refrigerant pipe20 (refer to FIG. 1) and liquid-side refrigerant flow dividing pipes 72Ato 72F which extend from the liquid-side refrigerant flow divider 71 andare connected to the liquid-side entrance communication spaces 85A to85F, respectively. Each of the liquid-side refrigerant flow dividingpipes 72A to 72F includes a capillary tube and has a length and an innerdiameter corresponding to a flow dividing ratio to each of the sub heatexchange sections 62A to 62F.

The gas-side flow dividing member 75 includes a gas-side refrigerantflow dividing header pipe 76 which is connected to the refrigerant pipe19 (refer to FIG. 1) and gas-side refrigerant flow dividing branch pipes77A to 77F which extend from the gas-side refrigerant flow dividingheader pipe 76 and are connected to the gas-side entrance communicationspaces 84A to 84F, respectively. The first gas-side entrancecommunication space 84A includes the first upper gas-side entrancecommunication space 84AU and the first lower gas-side entrancecommunication space 84AL. Thus, the first gas-side refrigerant flowdividing branch pipe 77A extending from the gas-side refrigerant flowdividing header pipe 76 also includes a first upper gas-side refrigerantflow dividing branch pipe 77AU and a first lower gas-side refrigerantflow dividing branch pipe 77AL.

An internal space of the second header collecting pipe 90 is verticallypartitioned by partition plates 91 so that return communication spaces92A to 92F respectively corresponding to the heat exchange sections 60Ato 60F are formed. Further, the first return communication space 92Acorresponding to the first heat exchange section 60A is verticallypartitioned into two spaces by a partition plate 93 so that a firstupper return communication space 92AU on the upper side and a firstlower return communication space 92AL on the lower side are formed. Theinternal space of the second header collecting pipe 90 is not limited tothe configuration merely partitioned by the partition plates 91, 93 asdescribed above, and alternatively may have a configuration designed forsatisfactorily maintaining a flow state of the refrigerant inside thesecond header collecting pipe 90.

Each of the return communication spaces 92A to 92F communicates with allthe flat pipes 63 constituting the corresponding one of the heatexchange sections 60A to 60F. More specifically, the second returncommunication space 92B communicates with all the eighteen flat pipes 63constituting the second heat exchange section 60B. The third returncommunication space 92C communicates with all the fifteen flat pipes 63constituting the third heat exchange section 60C. The fourth returncommunication space 92D communicates with all the thirteen flat pipes 63constituting the fourth heat exchange section 60D. The fifth returncommunication space 92E communicates with all the eleven flat pipes 63constituting the fifth heat exchange section 60E. The sixth returncommunication space 92F communicates with all the nine flat pipes 63constituting the sixth heat exchange section 60F. The first returncommunication space 92A communicates with all the twenty-one flat pipes63 constituting the first heat exchange section 60A. The first upperreturn communication space 92AU, which is the upper part of the firstreturn communication space 92A, communicates with top seventeen of thetwenty-one flat pipes 63 constituting the first heat exchange section60A. Further, the first lower return communication space 92AL, which isthe lower part of the first return communication space 92A, communicateswith bottom four of the twenty-one flat pipes 63 constituting the firstheat exchange section 60A including the lowermost flat pipe 63A.Further, top twelve of the seventeen flat pipes 63 communicating withthe first upper return communication space 92AU constitute the firstupper main heat exchange section 61AU which is one of the first mainheat exchange sections 61A, and the remaining five flat pipes 63constitute the first upper sub heat exchange section 62AU which is theupper part of the first sub heat exchange section 62A. Further, bottomtwo of the four flat pipes 63 communicating with the first lower returncommunication space 92AL including the lowermost flat pipe 63Aconstitute the first lower main heat exchange section 61AL which is theother first main heat exchange section 61A, and the remaining two flatpipes 63 constitute the first lower sub heat exchange section 62AL whichis the lower part of the first sub heat exchange section 62A.

Accordingly, each of the heat exchange sections 60A to 60F includes themain heat exchange sections 61A to 61F and the sub heat exchangesections 62A to 62F which are connected in series to the main heatexchange sections 61A to 61F at vertical positions different from themain heat exchange sections 61A to 61F. More specifically, the secondheat exchange section 60B has a configuration in which the twelve flatpipes 63 constituting the second main heat exchange section 61B whichcommunicates with the second gas-side entrance communication space 84Band the six flat pipes 63 constituting the second sub heat exchangesection 62B which is located directly below the second main heatexchange section 61B and communicates with the second liquid-sideentrance communication space 85B are connected in series through thesecond return communication space 92B. The third heat exchange section60C has a configuration in which the ten flat pipes 63 constituting thethird main heat exchange section 61C which communicates with the thirdgas-side entrance communication space 84C and the five flat pipes 63constituting the third sub heat exchange section 62C which is locateddirectly below the third main heat exchange section 61C and communicateswith the third liquid-side entrance communication space 85C areconnected in series through the third return communication space 92C.The fourth heat exchange section 60D has a configuration in which thenine flat pipes 63 constituting the fourth main heat exchange section61D which communicates with the fourth gas-side entrance communicationspace 84D and the four flat pipes 63 constituting the fourth sub heatexchange section 62D which is located directly below the fourth mainheat exchange section 61D and communicates with the fourth liquid-sideentrance communication space 85D are connected in series through thefourth return communication space 92D. The fifth heat exchange section60E has a configuration in which the seven flat pipes 63 constitutingthe fifth main heat exchange section 61E which communicates with thefifth gas-side entrance communication space 84E and the four flat pipes63 constituting the fifth sub heat exchange section 62E which is locateddirectly below the fifth main heat exchange section 61E and communicateswith the fifth liquid-side entrance communication space 85E areconnected in series through the fifth return communication space 92E.The sixth heat exchange section 60F has a configuration in which the sixflat pipes 63 constituting the sixth main heat exchange section 61Fwhich communicates with the sixth gas-side entrance communication space84F and the three flat pipes 63 constituting the sixth sub heat exchangesection 62F which is located directly below the sixth main heat exchangesection 61F and communicates with the sixth liquid-side entrancecommunication space 85F are connected in series through the sixth returncommunication space 92F. The first heat exchange section 60A has aconfiguration in which the fourteen flat pipes 63 constituting the firstmain heat exchange section 61A which communicates with the firstgas-side entrance communication space 84A and the seven flat pipes 63constituting the first sub heat exchange section 62A which communicateswith the first liquid-side entrance communication space 85A areconnected in series through the first return communication space 92A.The first heat exchange section 60A includes the two upper and lowerheat exchange sections 60AU, 60AL. The first upper heat exchange sectionAU has a configuration in which the twelve flat pipes 63 constitutingthe first upper main heat exchange section 61AU which communicates withthe first upper gas-side entrance communication space 84AU and the fiveflat pipes 63 constituting the first upper sub heat exchange section62AU which is located directly below the first upper main heat exchangesection 61AU and communicates with the first liquid-side entrancecommunication space 85A are connected in series through the first upperreturn communication space 92AU. The first lower heat exchange sectionAL has a configuration in which the two flat pipes 63 constituting thefirst lower main heat exchange section 61AL which communicates with thefirst lower gas-side entrance communication space 84AL including thelowermost flat pipe 63A and the two flat pipes 63 constituting the firstlower sub heat exchange section 62AL which is located directly above thefirst lower main heat exchange section 61AL and communicates with thefirst liquid-side entrance communication space 85A are connected inseries through the first lower return communication space 92AL.

In this manner, in one or more embodiments, the outdoor heat exchanger11 includes the flat pipes 63 which are vertically arrayed, each of theflat pipes 63 including the passage 63 b for the refrigerant formedinside thereof, and the fins 64 which partition a space between adjacentflat pipes 63 into a plurality of air flow passages through which airflows. The flat pipes 63 are divided into the heat exchange sections 60Ato 60F. Each of the heat exchange sections 60A to 60F include the mainheat exchange sections 61A to 61F and the sub heat exchange sections 62Ato 62F which are connected in series to the main heat exchange sections61A to 61F at vertical positions different from the main heat exchangesections 61A to 61F. Further, the first main heat exchange section 61Aof the first heat exchange section 60A including the lowermost flat pipe63A among the heat exchange sections 60A to 60F is disposed so as toinclude the lowermost flat pipe 63A.

Further, in one or more embodiments, all the heat exchange sections 60Bto 60F other than the first heat exchange section 60A are disposed abovethe first heat exchange section 60A. The first sub heat exchange section62A includes the first upper sub heat exchange section 62AU and thefirst lower sub heat exchange section 62AL which is located below thefirst upper sub heat exchange section 62AU. In addition, the first mainheat exchange section 61A includes the first upper main heat exchangesection 61AU which is connected to the first upper sub heat exchangesection 62AU above the first upper sub heat exchange section 62AU andthe first lower main heat exchange section 61AL which is connected tothe first lower sub heat exchange section 62AL below the first lower subheat exchange section 62AL.

Further, in one or more embodiments, the ratio of the number of flatpipes 63 (two) constituting the first lower main heat exchange section61AL to the number of flat pipes 63 (two) constituting the first lowersub heat exchange section 62AL (=2/2=1.0) is set smaller than the ratioof the number of flat pipes 63 (twelve) constituting the first uppermain heat exchange section 61AU to the number of flat pipes 63 (five)constituting the first upper sub heat exchange section 62AU (=12/5=2.4).The ratio of the number of flat pipes 63 constituting the first lowermain heat exchange section 61AL to the number of flat pipes 63constituting the first lower sub heat exchange section 62AL is notlimited to 1.0, but preferably within the range of 0.5 to 1.5. Further,the ratio of the number of flat pipes 63 constituting the first uppermain heat exchange section 61AU to the number of flat pipes 63constituting the first upper sub heat exchange section 62AU is notlimited to 2.4, but preferably within the range of 1.7 to 3.0.

Further, in one or more embodiments, the heat exchange sections 60A to60F are vertically arranged side by side, and, in the heat exchangesections 60B to 60F other than the first heat exchange section 60A, thesub heat exchange sections 62B to 62F are disposed below the main heatexchange sections 61B to 61F.

Next, the flow of the refrigerant in the outdoor heat exchanger 11having the above configuration will be described.

In the cooling operation, the outdoor heat exchanger 11 functions as aradiator for the refrigerant discharged from the compressor 8 (refer toFIG. 1).

The refrigerant discharged from the compressor 8 (refer to FIG. 1) isfed to the gas-side flow dividing member 75 through the refrigerant pipe19 (refer to FIG. 1). The refrigerant fed to the gas-side flow dividingmember 75 is divided into the gas-side refrigerant flow dividing branchpipes 77AU, 77AL, 77B to 77F from the gas-side refrigerant flow dividingheader pipe 76 and fed to the gas-side entrance communication spaces84AU, 84AL, 84B to 84F of the first header collecting pipe 80.

The refrigerant fed to each of the gas-side entrance communicationspaces 84AU, 84AL, 84B to 84F is divided into the flat pipes 63constituting the main heat exchange sections 61AU, 61AL, 61B to 61F ofthe corresponding heat exchange sections 60AU, 60AL, 60B to 60F. Therefrigerant fed to each flat pipe 63 dissipates heat by heat exchangewith outdoor air while flowing through the passage 63 b, and flows ofthe refrigerant merge with each other in each of the returncommunication spaces 92AU, 92AL, 92B to 92F of the second headercollecting pipe 90. That is, the refrigerant passes through the mainheat exchange sections 61AU, 61AL, 61B to 61F. At this time, therefrigerant dissipates heat until the refrigerant becomes a gas-liquidtwo-phase state or a liquid state close to a saturated state from asuperheated gas state.

The refrigerant merged in each of the return communication spaces 92AU,92L, 92B to 92F is divided into the flat pipes 63 constituting the subheat exchange sections 62AU, 62AL, 62B to 62F of the corresponding heatexchange sections 60AU, 60AL, 60B to 60F. The refrigerant fed to eachflat pipe 63 dissipates heat by heat exchange with outdoor air whileflowing through the passage 63 b, and flows of the refrigerant mergewith each other in each of the liquid-side entrance communication spaces85A to 85F of the first header collecting pipe 80. That is, therefrigerant passes through the sub heat exchange sections 62AU, 62AL,62B to 62F. At this time, the refrigerant further dissipates heat untilthe refrigerant becomes a subcooled liquid state from the gas-liquidtwo-phase state or the liquid state close to a saturated state.

The refrigerant fed to the liquid-side entrance communication spaces 85Ato 85F is fed to the liquid-side refrigerant flow dividing pipes 72A to72F of the liquid-side refrigerant flow dividing member 70, and flows ofthe refrigerant merge with each other in the liquid-side refrigerantflow divider 71. The refrigerant merged in the liquid-side refrigerantflow divider 71 is fed to the outdoor expansion valve 12 (refer toFIG. 1) through the refrigerant pipe 20 (refer to FIG. 1).

In the heating operation, the outdoor heat exchanger 11 functions as anevaporator for the refrigerant decompressed by the outdoor expansionvalve 12 (refer to FIG. 1).

The refrigerant decompressed by the outdoor expansion valve 12 is fed tothe liquid-side refrigerant flow dividing member 70 through therefrigerant pipe 20 (refer to FIG. 1). The refrigerant fed to theliquid-side refrigerant flow dividing member 70 is divided into theliquid-side refrigerant flow dividing pipes 72A to 72F from theliquid-side refrigerant flow divider 71 and fed to the liquid-sideentrance communication spaces 85A to 85F of the first header collectingpipe 80.

The refrigerant fed to each of the liquid-side entrance communicationspaces 85A to 85F is divided into the flat pipes 63 constituting the subheat exchange sections 62AU, 62AL, 62B to 62F of the corresponding heatexchange sections 60AU, 60AL, 60B to 60F. The refrigerant fed to eachflat pipe 63 evaporates by heat exchange with outdoor air while flowingthrough the passage 63 b, and flows of the refrigerant merge with eachother in each of the return communication spaces 92AU, 92AL, 92B to 92Fof the second header collecting pipe 90. That is, the refrigerant passesthrough the sub heat exchange sections 62AU, 62AL, 62B to 62F. At thistime, the refrigerant evaporates until the refrigerant becomes agas-liquid two-phase state having more gas components or a gas stateclose to a saturated state from a gas-liquid two-phase state having moreliquid components.

The refrigerant merged in each of the return communication spaces 92AU,92AL, 92B to 92F is divided into the flat pipes 63 constituting the mainheat exchange sections 61AU, 61AL, 61B to 61F of the corresponding heatexchange sections 60AU, 60AL, 60B to 60F. The refrigerant fed to eachflat pipe 63 evaporates (is heated) by heat exchange with outdoor airwhile flowing through the passage 63 b, and flows of the refrigerantmerge with each other in each of the gas-side entrance communicationspaces 84AU, 84AL, 84B to 84F of the first header collecting pipe 80.That is, the refrigerant passes through the main heat exchange sections61AU, 61AL, 61B to 61F. At this time, the refrigerant further evaporates(is heated) until the refrigerant becomes a superheated gas state fromthe gas-liquid two-phase state having more gas components or the gasstate close to a saturated state.

The refrigerant fed to the gas-side entrance communication spaces 84AU,84AL, 84B to 84F is fed to the gas-side refrigerant flow dividing branchpipes 77AU, 77AL, 77B to 77F of the gas-side refrigerant flow dividingmember 75, and flows of the refrigerant merge with each other in thegas-side refrigerant flow dividing header pipe 76. The refrigerantmerged in the gas-side refrigerant flow dividing header pipe 76 is fedto the suction side of the compressor 8 (refer to FIG. 1) through therefrigerant pipe 19 (refer to FIG. 1).

In the defrosting operation, the outdoor heat exchanger 11 functions asa radiator for the refrigerant discharged from the compressor 8 (referto FIG. 1) in a manner similar to the cooling operation. The flow of therefrigerant in the outdoor heat exchanger 11 in the defrosting operationis similar to that in the cooling operation. Thus, description thereofwill be omitted. However, differently from the cooling operation, therefrigerant mainly dissipates heat while melting frost adhered to theheat exchange sections 60AU, 60AL, 60B to 60F in the defrostingoperation.

(4) Characteristics

The outdoor heat exchanger 11 (heat exchanger) of one or moreembodiments has characteristics as described below.

<A>

As described above, the heat exchanger 11 of one or more embodimentsincludes the flat pipes 63 which are vertically arrayed, each of theflat pipes 63 including the passage 63 b for the refrigerant formedinside thereof, and the fins 64 which partition a space between adjacentflat pipes 63 into a plurality of air flow passages through which airflows. The flat pipes 63 are divided into the heat exchange sections 60Ato 60F. Each of the heat exchange sections 60A to 60F include the mainheat exchange sections 61A to 61F which are connected to the gas-sideentrance communication spaces 84A to 84F, respectively, and the sub heatexchange sections 62A to 62F which are connected in series to the mainheat exchange sections 61A to 61F at vertical positions different fromthe main heat exchange sections 61A to 61F and are connected to theliquid-side entrance communication spaces 85A to 85F, respectively.Further, in one or more embodiments, the first main heat exchangesection 61A of the first heat exchange section 60A including thelowermost flat pipe 63A among the heat exchange sections 60A to 60F isdisposed so as to include the lowermost flat pipe 63A.

On the other hand, in a conventional heat exchanger, a plurality of flatpipes are divided into a plurality of heat exchange sections which arevertically arranged side by side, and each of the heat exchange sectionsincludes a main heat exchange section and a sub heat exchange sectionwhich is connected in series to the main heat exchange section below themain heat exchange section. Thus, in the conventional heat exchanger,the sub heat exchange section of the lowermost one of the heat exchangesections is disposed so as to include the lowermost flat pipe (the flatpipe 63A in one or more embodiments). When such a conventional heatexchanger is employed in an air conditioner that performs a heatingoperation and a defrosting operation in a switching manner, the timerequired for melting frost adhered to the lowermost heat exchangesection tends to become longer than the time required for melting frostadhered to the heat exchange section located on the upper side relativeto the lowermost heat exchange section in the defrosting operation.First, the reason thereof will be described.

In the conventional configuration, when the heating operation (used asthe evaporator for the refrigerant) is switched to the defrostingoperation (used as the radiator for the refrigerant), the refrigerant ina liquid state tends to be accumulated in the lowermost sub heatexchange section including the lowermost flat pipe. Further, when thedefrosting operation is performed in such a condition, the refrigerantin a gas state first flows into the lowermost main heat exchange sectionand then flows into the lowermost sub heat exchange section. Thus, ittakes long time to evaporate the refrigerant in a liquid stateaccumulated in the lowermost sub heat exchange section. That is, it isassumed that, in the configuration of the conventional heat exchanger,the lowermost sub heat exchange section including the lowermost flatpipe located on the downstream side in the refrigerant flow in thedefrosting operation is one of the reasons why the time required formelting frost adhered to the lowermost heat exchange section becomeslong in the defrosting operation.

Further, in the conventional configuration, when the refrigerant in agas state is divided and flows into the main heat exchange section ofeach heat exchange section in the defrosting operation, a flow rate ofthe refrigerant in a gas state flowing into the lowermost heat exchangesection becomes lower than that in the upper heat exchange section dueto the influence of a liquid head of the refrigerant, which increasesthe time required for melting frost adhered to the lowermost heatexchange section. The degree of the liquid head is affected by theheight position of the flat pipe included in the sub heat exchangesection of the heat exchange section. Thus, when the lowermost sub heatexchange section includes the lowermost flat pipe, the liquid head ofthe refrigerant is large, and the flow rate of the refrigerant in a gasstate flowing into the lowermost heat exchange section in the defrostingoperation is further reduced. That is, it is assumed that, in theconfiguration of the conventional heat exchanger, a reduction in theflow rate of the refrigerant in a gas state flowing into the lowermostheat exchange section due to the liquid head of the refrigerant in thedefrosting operation is one of the reasons why the time required formelting frost adhered to the lowermost heat exchange section becomeslong in the defrosting operation.

Further, in the conventional configuration, the lower end part of thefin close to the lowermost flat pipe is in contact with a drain pan (thebottom frame 42 in one or more embodiments). Thus, heat dissipation fromthe lowermost sub heat exchange section including the lowermost flatpipe to the drain pan tends to occur. When the defrosting operation isperformed in such a condition, the heat dissipation from the lowermostsub heat exchange section to the drain pan hinders a temperature rise inthe lowermost heat exchange section as compared to the upper heatexchange section, which increases the time required for melting frostadhered to the lowermost heat exchange section. That is, it is assumedthat, in the configuration of the conventional heat exchanger, heatdissipation from the lowermost sub heat exchange section including thelowermost flat pipe to the drain pan is one of the reasons why the timerequired for melting frost adhered to the lowermost heat exchangesection becomes long in the defrosting operation.

In this manner, it is assumed that, in the conventional heat exchanger,when the heat exchanger is employed in the air conditioner that performsthe heating operation and the defrosting operation in a switchingmanner, the time required for melting frost adhered to the lowermostheat exchange section is longer than the time required for melting frostadhered to the heat exchange section located on the upper side relativeto the lowermost heat exchange section because the lowermost sub heatexchange section includes the lowermost flat pipe.

Thus, in one or more embodiments, differently from the conventional heatexchanger, as described above, the first main heat exchange section 61Aof the first heat exchange section 60A including the lowermost flat pipe63A among the heat exchange sections 60A to 60F is disposed so as toinclude the lowermost flat pipe 63A.

As described above, when the heat exchanger 11 having such aconfiguration is employed in the air conditioner 1 which performs theheating operation and the defrosting operation in a switching manner, asillustrated in FIG. 8, the refrigerant in a gas-liquid two-phase stateflows into the first sub heat exchange section 62A, is heated whilepassing through the first sub heat exchange section 62A and the firstmain heat exchange section 61A including the lowermost flat pipe 63A inthat order, and flows out of the first heat exchange section 60A in theheating operation (used as the evaporator for the refrigerant) whenattention is paid to the first heat exchange section 60A. Further, inthe defrosting operation (used as the radiator for the refrigerant), asillustrated in FIG. 9, the refrigerant in a gas state flows into thefirst main heat exchange section 61A, is cooled while passing throughthe first main heat exchange section 61A including the lowermost flatpipe 63A and the first sub heat exchange section 62A in that order, andflows out of the first heat exchange section 60A. That is, in one ormore embodiments, the first main heat exchange section 61A including thelowermost flat pipe 63A is located on the upstream side in therefrigerant flow in the defrosting operation. Thus, in one or moreembodiments, it is possible to allow the refrigerant in a gas state toflow into the first main heat exchange section 61A including thelowermost flat pipe 63A to actively heat and evaporate the refrigerantin a liquid state accumulated in the lowermost first sub heat exchangesection 62A and promptly increase the temperature in the lowermost firstheat exchange section 60A. Accordingly, it is possible to shorten thetime required for melting frost adhered to the lowermost heat exchangesection 63A in the defrosting operation as compared to the case wherethe conventional heat exchanger is employed.

In this manner, in one or more embodiments, it is possible to shortenthe time required for melting frost adhered to the lowermost heatexchange section 60A in the defrosting operation by employing the heatexchanger 11 having the above configuration in the air conditioner 1which performs the heating operation and the defrosting operation in aswitching manner.

<B>

Further, as described above, in the heat exchanger 11 of one or moreembodiments, all the heat exchange sections 60B to 60F other than thefirst heat exchange section 60A are disposed above the first heatexchange section 60A. Further, the first sub heat exchange section 62Aincludes the first upper sub heat exchange section 62AU and the firstlower sub heat exchange section 62AL which is located below the firstupper sub heat exchange section 62AU. In addition, the first main heatexchange section 61A includes the first upper main heat exchange section61AU which is connected to the first upper sub heat exchange section62AU above the first upper sub heat exchange section 62AU and the firstlower main heat exchange section 61AL which is connected to the firstlower sub heat exchange section 62AL below the first lower sub heatexchange section 62AL.

In this configuration, when attention is paid to the first heat exchangesection 60A, the refrigerant in a gas-liquid two-phase state flows intothe first upper sub heat exchange section 62AU and the first lower subheat exchange section 62AL as illustrated in FIG. 8 in the heatingoperation (used as the evaporator for the refrigerant). Then, therefrigerant in a gas-liquid two-phase state flowing into the first uppersub heat exchange section 62AU is heated while passing through the firstupper sub heat exchange section 62AU and the first upper main heatexchange section 61AU located above the first upper sub heat exchangesection 62AU in that order, and flows out of the first heat exchangesection 60A. The refrigerant in a gas-liquid two-phase state flowinginto the first lower sub heat exchange section 62AL is heated whilepassing through the first lower sub heat exchange section 62AL and thefirst lower main heat exchange section 61AL located below the firstlower sub heat exchange section 62AL in that order, and flows out of thefirst heat exchange section 60A. Further, in the defrosting operation(used as the radiator for the refrigerant), as illustrated in FIG. 9,the refrigerant in a gas state flows into the first upper main heatexchange section 61AU and the first lower main heat exchange section61AL. Then, the refrigerant in a gas state flowing into the first uppermain heat exchange section 61AU is cooled while passing through thefirst upper main heat exchange section 61AU and the first upper sub heatexchange section 62AU located below the first upper main heat exchangesection 61AU in that order, and flows out of the first heat exchangesection 60A. The refrigerant in a gas state flowing into the first lowermain heat exchange section 61AL is cooled while passing through thefirst lower main heat exchange section 61AL and the first lower sub heatexchange section 62AL located above the first lower main heat exchangesection 61AL in that order, and flows out of the first heat exchangesection 60A.

<C>

Further, as described above, in the heat exchanger 11 of one or moreembodiments, the ratio of the number of flat pipes 63 constituting thefirst lower main heat exchange section 61AL to the number of flat pipes63 constituting the first lower sub heat exchange section 62AL is setsmaller than the ratio of the number of flat pipes 63 constituting thefirst upper main heat exchange section 61AU to the number of flat pipes63 constituting the first upper sub heat exchange section 62AU.

The above configuration of <B> includes the first heat exchange section60A in which the first upper sub heat exchange section 62AU is disposedbelow the first upper main heat exchange section 61AU, and the firstlower main heat exchange section 61AL is disposed below the first lowersub heat exchange section 62AL. In this configuration, as illustrated inFIG. 8, the first lower sub heat exchange section 62AL and the firstlower main heat exchange section 61AL (the first lower heat exchangesection 60AL) in the first heat exchange section 60A function as aso-called down flow type evaporator in which the refrigerant passesthrough the first lower sub heat exchange section 62AL and then passesthrough the first lower main heat exchange section 61AL disposed belowthe first lower sub heat exchange section 62AL in the heating operation(used as the evaporator for the refrigerant). In the down flow typeevaporator, when a fluid in a gas-liquid two-phase state is divided whenbeing fed downward, a drift of the fluid tends to occur. Also in thefirst lower sub heat exchange section 62AL and the first lower main heatexchange section 61AL, the refrigerant is divided when being feddownward from the flat pipes 63 constituting the first lower sub heatexchange section 62AL to the flat pipes 63 constituting the first lowermain heat exchange section 61AL. Thus, there is a possibility that adrift of the refrigerant occurs. At this time, when the ratio of thenumber of flat pipes 63 constituting the first lower main heat exchangesection 61AL to the number of flat pipes 63 constituting the first lowersub heat exchange section 62AL increases, the possibility of theoccurrence of a drift of the refrigerant increases.

Thus, in one or more embodiments, as described above, the ratio of thenumber of flat pipes 63 constituting the first lower main heat exchangesection 61AL to the number of flat pipes 63 constituting the first lowersub heat exchange section 62AL is set smaller than the ratio of thenumber of flat pipes 63 constituting the first upper main heat exchangesection 61AU to the number of flat pipes 63 constituting the first uppersub heat exchange section 62AU in the first heat exchange section 60A.

Accordingly, in one or more embodiments, when the refrigerant is feddownward from the flat pipes 63 constituting the first lower sub heatexchange section 62AL to the flat pipes 63 constituting the first lowermain heat exchange section 61AU in the heating operation (used as theevaporator for the refrigerant), it is possible to suppress a drift ofthe refrigerant caused by the division of the refrigerant.

<D>

Further, as described above, in the heat exchanger 11 of one or moreembodiments, the heat exchange sections 60A to 60F are verticallyarranged side by side. Further, in the heat exchange sections 60B to 60Fother than the first heat exchange section 60A, the sub heat exchangesections 62B to 62F are disposed below the main heat exchange sections61B to 61F.

In this configuration, when attention is paid to the heat exchangesections 60B to 60F other than the first heat exchange section 60A, therefrigerant in a gas-liquid two-phase state flows into the sub heatexchange sections 62B to 62F, is heated while passing through the subheat exchange sections 62B to 62F and the main heat exchange sections61B to 61F located above the sub heat exchange sections 62B to 62F inthat order, and flows out of the heat exchange sections 60B to 60F inthe heating operation (used as the evaporator for the refrigerant).Further, in the defrosting operation (used as the radiator for therefrigerant), the refrigerant in a gas state flows into the main heatexchange sections 61B to 61F, is cooled while passing through the mainheat exchange sections 61B to 61F and the sub heat exchange sections 62Bto 62F located below the main heat exchange sections 61B to 61F in thatorder, and flows out of the heat exchange sections 60B to 60F.

(5) Modifications

<A>

In the outdoor heat exchanger 11 (heat exchanger) of the aboveembodiments, the configuration in which the main heat exchange section61A is disposed so as to include the lowermost flat pipe 63A in thelowermost first heat exchange section 60A including the lowermost flatpipe 63A is achieved by dividing the first heat exchange section 60Ainto the first upper heat exchange section 60AU and the first lower heatexchange section 60AL in which the first lower main heat exchangesection 61AL is disposed so as to include the lowermost flat pipe 63A(refer to FIGS. 6 to 9). This configuration is obtained by disposing thetwo partition plates 86 on the first header collecting pipe 80 so as topartition the first entrance communication space 82A corresponding tothe first heat exchange section 60A into the three entrancecommunication spaces 84AU, 85A, 84AL and disposing the partition plate93 on the second header collecting pipe 90 so as to partition the firstreturn communication space 92A corresponding to the first heat exchangesection 60A into the two return communication spaces 92AU, 92AL. In thisconfiguration, the first liquid-side entrance communication space 85A isa liquid-side entrance communication space common between the firstupper heat exchange section 60AU and the first lower heat exchangesection 60AL. In this point, the first upper heat exchange section 60AUand the first lower heat exchange section 60AL are not independent ofeach other.

However, the configuration in which the main heat exchange section 61Ais disposed so as to include the lowermost flat pipe 63A in thelowermost first heat exchange section 60A including the lowermost flatpipe 63A is not limited to the above configuration.

For example, in the heat exchanger 11 of the above embodiments, thefirst header collecting pipe 80 may further include a partition platethat vertically partitions the first liquid-side entrance communicationspace 85A into two spaces to form two liquid-side entrance communicationspaces so that the first upper heat exchange section 60AU and the firstlower heat exchange section 60AL are independent of each other.

Specifically, in an outdoor heat exchanger 11 of the presentmodification, as illustrated in FIGS. 10 to 14, a plurality of flatpipes 63 are divided into a plurality of heat exchange sections 60A to60G (in the present modification, seven heat exchange sections) whichare vertically arranged side by side. Specifically, in the presentmodification, the first heat exchange section 60A which is the lowermostheat exchange section, the second heat exchange section 60B, . . . , thesixth heat exchange section 60F, and the seventh heat exchange section60G are formed in that order from bottom to top. The first heat exchangesection 60A includes four flat pipes 63 including the lowermost flatpipe 63A. The second heat exchange section 60B includes seventeen flatpipes 63. The third heat exchange section 60C includes eighteen flatpipes 63. The fourth heat exchange section 60D includes fifteen flatpipes 63. The fifth heat exchange section 60E includes thirteen flatpipes 63. The sixth heat exchange section 60F includes eleven flat pipes63. The seventh heat exchange section 60G includes nine flat pipes 63.

An internal space of the first header collecting pipe 80 is verticallypartitioned by a partition plate 81 so that entrance communicationspaces 82A to 82G respectively corresponding to the heat exchangesections 60A to 60G are formed. Further, each of the entrancecommunication spaces 82A to 82G is vertically partitioned into twospaces by a partition plate 83. Accordingly, upper gas-side entrancecommunication spaces 84B to 84G and lower liquid-side entrancecommunication spaces 85B to 85G are formed in the entrance communicationspaces 82B to 82G except the first entrance communication space 82Acorresponding to the first heat exchange section 60A. An upper firstliquid-side entrance communication space 85A and a lower first gas-sideentrance communication space 84A are formed in the first entrancecommunication space 82A corresponding to the first heat exchange section60A.

The second gas-side entrance communication space 84B communicates withtop twelve of the flat pipes 63 constituting the second heat exchangesection 60B. The second liquid-side entrance communication space 85Bcommunicates with the remaining five of the flat pipes 63 constitutingthe second heat exchange section 60B. The third gas-side entrancecommunication space 84C communicates with top twelve of the flat pipes63 constituting the third heat exchange section 60C. The thirdliquid-side entrance communication space 85C communicates with theremaining six of the flat pipes 63 constituting the third heat exchangesection 60C. The fourth gas-side entrance communication space 84Dcommunicates with top ten of the flat pipes 63 constituting the fourthheat exchange section 60D. The fourth liquid-side entrance communicationspace 85D communicates with the remaining five of the flat pipes 63constituting the fourth heat exchange section 60D. The fifth gas-sideentrance communication space 84E communicates with top nine of the flatpipes 63 constituting the fifth heat exchange section 60E. The fifthliquid-side entrance communication space 85E communicates with theremaining four of the flat pipes 63 constituting the fifth heat exchangesection 60E. The sixth gas-side entrance communication space 84Fcommunicates with top seven of the flat pipes 63 constituting the sixthheat exchange section 60F. The sixth liquid-side entrance communicationspace 85F communicates with the remaining four of the flat pipes 63constituting the sixth heat exchange section 60F. The seventh gas-sideentrance communication space 84G communicates with top six of the flatpipes 63 constituting the seventh heat exchange section 60G. The seventhliquid-side entrance communication space 85G communicates with theremaining three of the flat pipes 63 constituting the seventh heatexchange section 60G. The first gas-side entrance communication space84A communicates with bottom two of the flat pipes 63 constituting thefirst heat exchange section 60A including the lowermost flat pipe 63A.The first liquid-side entrance communication space 85A communicates withthe remaining two of the flat pipes 63 constituting the first heatexchange section 60A.

The flat pipes 63 communicating with the gas-side entrance communicationspaces 84A to 84G are defined as main heat exchange sections 61A to 61G,and the flat pipes 63 communicating with the liquid-side entrancecommunication spaces 85A to 85G are defined as sub heat exchangesections 62A to 62G. More specifically, in the second entrancecommunication space 82B, the second gas-side entrance communicationspace 84B communicates with top twelve of the flat pipes 63 constitutingthe second heat exchange section 60B (the second main heat exchangesection 61B), and the second liquid-side entrance communication space85B communicates with the remaining five of the flat pipes 63constituting the second heat exchange section 60B (the second sub heatexchange section 62B). In the third entrance communication space 82C,the third gas-side entrance communication space 84C communicates withtop twelve of the flat pipes 63 constituting the third heat exchangesection 60C (the third main heat exchange section 61C), and the thirdliquid-side entrance communication space 85C communicates with theremaining six of the flat pipes 63 constituting the third heat exchangesection 60C (the third sub heat exchange section 62C). In the fourthentrance communication space 82D, the fourth gas-side entrancecommunication space 84D communicates with top ten of the flat pipes 63constituting the fourth heat exchange section 60D (the fourth main heatexchange section 61D), and the fourth liquid-side entrance communicationspace 85D communicates with the remaining five of the flat pipes 63constituting the fourth heat exchange section 60D (the fourth sub heatexchange section 62D). In the fifth entrance communication space 82E,the fifth gas-side entrance communication space 84E communicates withtop nine of the flat pipes 63 constituting the fifth heat exchangesection 60E (the fifth main heat exchange section 61E), and the fifthliquid-side entrance communication space 85E communicates with theremaining four of the flat pipes 63 constituting the fifth heat exchangesection 60E (the fifth sub heat exchange section 62E). In the sixthentrance communication space 82F, the sixth gas-side entrancecommunication space 84F communicates with top seven of the flat pipes 63constituting the sixth heat exchange section 60F (the sixth main heatexchange section 61F), and the sixth liquid-side entrance communicationspace 85F communicates with the remaining four of the flat pipes 63constituting the fifth heat exchange section 60F (the sixth sub heatexchange section 62F). In the seventh entrance communication space 82G,the seventh gas-side entrance communication space 84G communicates withtop six of the flat pipes 63 constituting the seventh heat exchangesection 60G (the seventh main heat exchange section 61G), and theseventh liquid-side entrance communication space 85G communicates withthe remaining three of the flat pipes 63 constituting the seventh heatexchange section 60G (the seventh sub heat exchange section 62G). In thefirst entrance communication space 82A, the first gas-side entrancecommunication space 84A communicates with bottom two of the flat pipes63 constituting the first heat exchange section 60A including thelowermost flat pipe 63A (the first main heat exchange section 61A), andthe first liquid-side entrance communication space 85A communicates withthe remaining two of the flat pipes 63 constituting the first heatexchange section 60A (the first sub heat exchange section 62A).

A liquid-side flow dividing member 70 which divides and feeds therefrigerant fed from the outdoor expansion valve 12 (refer to FIG. 1)into the liquid-side entrance communication spaces 85A to 85G in theheating operation and a gas-side flow dividing member 75 which dividesand feeds the refrigerant fed from the compressor 8 (refer to FIG. 1)into the gas-side entrance communication spaces 84A to 84G in thecooling operation are connected to the first header collecting pipe 80.

The liquid-side flow dividing member 70 includes a liquid-siderefrigerant flow divider 71 which is connected to the refrigerant pipe20 (refer to FIG. 1) and liquid-side refrigerant flow dividing pipes 72Ato 72G which extend from the liquid-side refrigerant flow divider 71 andare connected to the liquid-side entrance communication spaces 85A to85G, respectively. Each of the liquid-side refrigerant flow dividingpipes 72A to 72G includes a capillary tube and has a length and an innerdiameter corresponding to a flow dividing ratio to each of the sub heatexchange sections 62A to 62G.

The gas-side flow dividing member 75 includes a gas-side refrigerantflow dividing header pipe 76 which is connected to the refrigerant pipe19 (refer to FIG. 1) and gas-side refrigerant flow dividing branch pipes77A to 77G which extend from the gas-side refrigerant flow dividingheader pipe 76 and are connected to the gas-side entrance communicationspaces 84A to 84G, respectively.

An internal space of the second header collecting pipe 90 is verticallypartitioned by partition plates 91 so that return communication spaces92A to 92G respectively corresponding to the heat exchange sections 60Ato 60G are formed. The internal space of the second header collectingpipe 90 is not limited to the configuration merely partitioned by thepartition plates 91 as described above, and alternatively may have aconfiguration designed for satisfactorily maintaining a flow state ofthe refrigerant inside the second header collecting pipe 90.

Each of the return communication spaces 92A to 92G communicates with allthe flat pipes 63 constituting the corresponding one of the heatexchange sections 60A to 60G. More specifically, the second returncommunication space 92B communicates with all the seventeen flat pipes63 constituting the second heat exchange section 60B. The third returncommunication space 92C communicates with all the eighteen flat pipes 63constituting the third heat exchange section 60C. The fourth returncommunication space 92D communicates with all the fifteen flat pipes 63constituting the fourth heat exchange section 60D. The fifth returncommunication space 92E communicates with all the thirteen flat pipes 63constituting the fifth heat exchange section 60E. The sixth returncommunication space 92F communicates with all the eleven flat pipes 63constituting the sixth heat exchange section 60F. The seventh returncommunication space 92G communicates with all the nine flat pipes 63constituting the seventh heat exchange section 60G. The first returncommunication space 92A communicates with all the four flat pipes 63constituting the first heat exchange section 60A including the lowermostflat pipe 63A.

Accordingly, each of the heat exchange sections 60A to 60G include themain heat exchange sections 61A to 61G and the sub heat exchangesections 62A to 62G which are connected in series to the main heatexchange sections 61A to 61G at vertical positions different from themain heat exchange sections 61A to 61G. More specifically, the secondheat exchange section 60B has a configuration in which the twelve flatpipes 63 constituting the second main heat exchange section 61B whichcommunicates with the second gas-side entrance communication space 84Band the five flat pipes 63 constituting the second sub heat exchangesection 62B which is located directly below the second main heatexchange section 61B and communicates with the second liquid-sideentrance communication space 85B are connected in series through thesecond return communication space 92B. The third heat exchange section60C has a configuration in which the twelve flat pipes 63 constitutingthe third main heat exchange section 61C which communicates with thethird gas-side entrance communication space 84C and the six flat pipes63 constituting the third sub heat exchange section 62C which is locateddirectly below the third main heat exchange section 61C and communicateswith the third liquid-side entrance communication space 85C areconnected in series through the third return communication space 92C.The fourth heat exchange section 60D has a configuration in which theten flat pipes 63 constituting the fourth main heat exchange section 61Dwhich communicates with the fourth gas-side entrance communication space84D and the five flat pipes 63 constituting the fourth sub heat exchangesection 62D which is located directly below the fourth main heatexchange section 61D and communicates with the fourth liquid-sideentrance communication space 85D are connected in series through thefourth return communication space 92D. The fifth heat exchange section60E has a configuration in which the nine flat pipes 63 constituting thefifth main heat exchange section 61E which communicates with the fifthgas-side entrance communication space 84E and the four flat pipes 63constituting the fifth sub heat exchange section 62E which is locateddirectly below the fifth main heat exchange section 61E and communicateswith the fifth liquid-side entrance communication space 85E areconnected in series through the fifth return communication space 92E.The sixth heat exchange section 60F has a configuration in which theseven flat pipes 63 constituting the sixth main heat exchange section61F which communicates with the sixth gas-side entrance communicationspace 84F and the four flat pipes 63 constituting the sixth sub heatexchange section 62F which is located directly below the sixth main heatexchange section 61F and communicates with the sixth liquid-sideentrance communication space 85F are connected in series through thesixth return communication space 92F. The seventh heat exchange section60G has a configuration in which the six flat pipes 63 constituting theseventh main heat exchange section 61G which communicates with theseventh gas-side entrance communication space 84G and the three flatpipes 63 constituting the seventh sub heat exchange section 62G which islocated directly below the seventh main heat exchange section 61G andcommunicates with the seventh liquid-side entrance communication space85G are connected in series through the seventh return communicationspace 92G. The first heat exchange section 60A has a configuration inwhich the two flat pipes 63 constituting the first main heat exchangesection 61A which communicates with the first gas-side entrancecommunication space 84A including the lowermost flat pipe 63A and thetwo flat pipes 63 constituting the first sub heat exchange section 62Awhich is located directly above the first main heat exchange section 61Aand communicates with the first liquid-side entrance communication space85A are connected in series through the first return communication space92A.

In this manner, in the present modification, the heat exchanger 11includes the flat pipes 63 which are vertically arrayed, each of theflat pipes 63 including the passage 63 b for the refrigerant formedinside thereof, and the fins 64 which partition a space between adjacentflat pipes 63 into a plurality of air flow passages through which airflows in a manner similar to the above embodiments. The flat pipes 63are divided into the heat exchange sections 60A to 60G. Each of the heatexchange sections 60A to 60G include the main heat exchange sections 61Ato 61G and the sub heat exchange sections 62A to 62G which are connectedin series to the main heat exchange sections 61A to 61G at verticalpositions different from the main heat exchange sections 61A to 61G.Further, the first main heat exchange section 61A of the first heatexchange section 60A including the lowermost flat pipe 63A among theheat exchange sections 60A to 60G is disposed so as to include thelowermost flat pipe 63A.

Thus, in the configuration of the present modification, the timerequired for melting frost adhered to the lowermost heat exchangesection 60A can be shortened in the defrosting operation in a mannersimilar to the above embodiments.

Further, in the present modification, all the heat exchange sections 60Bto 60G other than the first heat exchange section 60A are disposed abovethe first heat exchange section 60A. Further, in the first heat exchangesection 60A, the first main heat exchange section 61A is disposed belowthe first sub heat exchange section 62A.

In the configuration of the present modification, when attention is paidto the first heat exchange section 60A, as illustrated in FIG. 13, therefrigerant in a gas-liquid two-phase state flows into the first subheat exchange section 62A, is heated while passing through the first subheat exchange section 62A and the first main heat exchange section 61Alocated below the first sub heat exchange section 62A in that order, andflows out of the first heat exchange section 60A in the heatingoperation (used as the evaporator for the refrigerant). Further, in thedefrosting operation (used as the radiator for the refrigerant), asillustrated in FIG. 14, the refrigerant in a gas state flows into thefirst main heat exchange section 61A, is cooled while passing throughthe first main heat exchange section 61A and the first sub heat exchangesection 62A located above the first main heat exchange section 61A inthat order, and flows out of the first heat exchange section 60A.

The above configuration provides the first heat exchange section 60A inwhich the first main heat exchange section 61A is disposed below thefirst sub heat exchange section 62A. Thus, in a manner similar to theabove embodiments, as illustrated in FIG. 13, the first heat exchangesection 60A functions as a so-called down flow type evaporator in whichthe refrigerant passes through the first sub heat exchange section 62Aand then passes through the first main heat exchange section 61Adisposed below the first sub heat exchange section 62A in the heatingoperation (used as the evaporator for the refrigerant). Also in thefirst heat exchange section 60A of the present modification, therefrigerant is divided when being fed downward from the flat pipes 63constituting the first sub heat exchange section 62A to the flat pipes63 constituting the first main heat exchange section 61A. Thus, there isa possibility that a drift of the refrigerant occurs. At this time, whenthe ratio of the number of flat pipes 63 constituting the first mainheat exchange section 61A to the number of flat pipes 63 constitutingthe first sub heat exchange section 62A increases, the possibility ofthe occurrence of a drift of the refrigerant increases.

Thus, in the present modification, the ratio of the number of flat pipes63 (two) constituting the first main heat exchange section 61A to thenumber of flat pipes 63 (two) constituting the first sub heat exchangesection 62A (=2/2=1.0) is set smaller than the ratio of the number offlat pipes 63 (six to twelve) constituting each of the main heatexchange sections 61A to 61G to the number of flat pipes 63 (three tosix) constituting each of the sub heat exchange sections 62B to 62G inthe other heat exchange sections 60B to 60G (=7/4 to 12/5=1.8 to 2.4).The ratio of the number of flat pipes 63 constituting the first mainheat exchange section 61A to the number of flat pipes 63 constitutingthe first sub heat exchange section 62A is not limited to 1.0, butpreferably within the range of 0.5 to 1.5. Further, the ratio of thenumber of flat pipes 63 constituting each of the other main heatexchange sections 61B to 61G to the number of flat pipes 63 constitutingeach of the other sub heat exchange sections 62B to 62G is not limitedto 1.8 to 2.4, but preferably within the range of 1.7 to 3.0.

Accordingly, in the present modification, when the refrigerant is feddownward from the flat pipes 63 constituting the first sub heat exchangesection 62A to the flat pipes 63 constituting the first main heatexchange section 61A in the heating operation (used as the evaporatorfor the refrigerant), it is possible to suppress a drift of therefrigerant caused by the division of the refrigerant in a mannersimilar to the above embodiments.

<B>

In the above embodiments and the modification <A>, the present inventionis applied to the outdoor heat exchanger 11 including six or seven heatexchange sections. However, the present invention is not limitedthereto. The number of heat exchange sections may be less than six ormore than seven.

Further, the number of flat pipes 63 constituting each of the heatexchange sections 60A to 60G and the ratio between the number of flatpipes 63 of each of the main heat exchange sections 61A to 61G and thenumber of flat pipes 63 of each of the sub heat exchange sections 62A to62G in each of the heat exchange sections 60A to 60G are not limited tothe number and the ratio in the above embodiments and the modification<A>.

Further, in the above embodiments and the modification <A>, the presentinvention is applied to the outdoor heat exchanger 11 disposed on thetop blow-out type outdoor unit 2. However, the present invention may beapplied to an outdoor heat exchanger disposed on an outdoor unit ofanother type.

INDUSTRIAL APPLICABILITY

The present invention is widely applicable to a heat exchanger includinga plurality of flat pipes vertically arrayed, each of the flat pipesincluding a passage for a refrigerant formed inside thereof, and aplurality of fins that partition a space between adjacent flat pipesinto a plurality of air flow passages through which air flows.

REFERENCE SIGNS LIST

-   11 outdoor heat exchanger (heat exchanger)-   60A to 60G heat exchange section-   60A first heat exchange section-   61A to 61G main heat exchange section-   61A first main heat exchange section-   61AU first upper main heat exchange section-   61AL first lower main heat exchange section-   62A to 62G sub heat exchange section-   62A first sub heat exchange section-   62AU first upper sub heat exchange section-   62AL first lower sub heat exchange section-   63 flat pipe-   63 b passage-   64 fin

Although the disclosure has been described with respect to only alimited member of embodiments, those skilled in the art, having benefitof this disclosure, will appreciate that various other embodiments maybe devised without departing from the scope of the present invention.Accordingly, the scope of the invention should be limited only by theattached claims.

1.-6. (canceled)
 7. A heat exchanger comprising: flat pipes verticallyarrayed, wherein each of the flat pipes includes a passage for arefrigerant; and fins that partition a space between adjacent ones ofthe flat pipes into air flow passages, wherein the flat pipes aredivided into heat exchange sections, each of the heat exchange sectionsincludes: a main heat exchange section connected to a gas-side entrancecommunication space, and a sub heat exchange section that is connected:in series to the main heat exchange section at a vertical positiondifferent from the main heat exchange section, and to a liquid-sideentrance communication space, and a first heat exchange section amongthe heat exchange sections includes a lowermost one of the flat pipes,the main heat exchange section of the first heat exchange section is afirst main heat exchange section, the sub heat exchange section of thefirst heat exchange section is a first sub heat exchange section, andthe first main heat exchange section is disposed to include thelowermost flat pipe.
 8. The heat exchanger according to claim 7, whereinall the heat exchange sections other than the first heat exchangesection are disposed above the first heat exchange section, and thefirst main heat exchange section is disposed below the first sub heatexchange section in the first heat exchange section.
 9. The heatexchanger according to claim 7, wherein a ratio of a number of the flatpipes constituting the first main heat exchange section to a number ofthe flat pipes constituting the first sub heat exchange section issmaller than a ratio of a number of the flat pipes constituting the mainheat exchange section to a number of the flat pipes constituting the subheat exchange section in the heat exchange sections other than the firstheat exchange section.
 10. The heat exchanger according to claim 7,wherein all the heat exchange sections other than the first heatexchange section are disposed above the first heat exchange section, thefirst sub heat exchange section includes a first upper sub heat exchangesection and a first lower sub heat exchange section disposed below thefirst upper sub heat exchange section, and the first main heat exchangesection includes: a first upper main heat exchange section connected tothe first upper sub heat exchange section above the first upper sub heatexchange section, and a first lower main heat exchange section connectedto the first lower sub heat exchange section below the first lower subheat exchange section.
 11. The heat exchanger according to claim 10,wherein a ratio of a number of the flat pipes constituting the firstlower main heat exchange section to a number of the flat pipesconstituting the first lower sub heat exchange section is smaller than aratio of a number of the flat pipes constituting the first upper mainheat exchange section to a number of the flat pipes constituting thefirst upper sub heat exchange section.
 12. The heat exchanger accordingto claim 7, wherein the heat exchange sections are vertically disposedside by side, and the sub heat exchange section is disposed below themain heat exchange section in the heat exchange sections other than thefirst heat exchange section.